1. R&D for SciFi calorimeters and STAR forward instrumentation upgrades.
O.Tsai (UCLA) March 9, 2011

2. Where we are?
UCLA has proposal for generic calorimetric technology for dedicated EIC detector.
New technique. Need to be proven. Plan for the first year of R&D was to build and test 6x6 matrix EMC. Targeted resolution 10%/√(E).
In line with STAR decadal plan we want to extend the scope of the first stage and include some tasks for integrated EM+HAD SPACAL type R&D.

3. Motivations for calorimetry R&D:
Develop simple, cost effective, flexible techniques to build compact sampling calorimeters with good characteristics.
Simple – to the level that a typical university group can build it without heavy investments in “infrastructure”.
Cost effective – fraction of the cost of crystals.
Flexible – tunable for particular experimental requirements.
Idea:
Mix tungsten powder and scintillating fibers.
Why SciFi type?
Cost effectiveness, flexibility and simplicity is obvious pluses, one can add that with simple technique which is easily transferable to a different university groups is a good
way to keep people involved in real construction and later on commissioning, operation
and data analysis, i.e. it is not just a computing science…
Say that it is started as pure conceptual development in 2003.

4. Why ScFi type?
“Speed of response, compensation, linearity, good energy resolution for electromagnetic and hadronic showers, uniformity of response as a function of impact point and angle, hermeticity, ease of lateral segmentation, spatial resolution, low noise, and sensitivity to minimum ionizing particles”
NIM A302(1991) “Electron-pion discrimination with scintillating fiber calorimeter”

5. R.Wigmans , Calor 2010
Fiber calorimeters have a very good record.
SPACAL still holds the record for best hadronic resolution.
DREAM aims to set new standards in high resolution calorimetry.

6. SPACAL, as an example Parameters: Eff. Radiation Length 7.5 mm
Eff. Rm mm
Eff. Nucl. Int. Length cm
Density g/cm^3
Sampling Fraction %
Depth Int. length
Width Int. length
Granularity (eff. Radius) 39mm
NIM A305 (1991) 55-70

7. + SPACAL as an example. Compensation Speed of response
Connection to slide (4) SPACAL is easily outperform CMS and ATLAS systems for jets <100 GeV,
eRHIC domain.
Particle identification additional benefit (eRHIC I think wants it DIRC etc).
D.Acosta et al., NIM A302 (1991) 36-46
SPACAL had fast (25ns) ‘electron’ trigger.
e/h rejection ~1000 at 80GeV, e efficiency ~90%
R.Wigmans, NIM A494 (2002)

8. “Localizing particles showering in a Spaghetti Calorimeter” NIM A305(1991) 55-70
Ease of lateral segmentation
Good position resolution and non-projectivity
e/h rejection is ~ 1000
e/h rejection is ~ 10000, e efficiency 98%

9. What is in the STAR Decadal Plan.
We want it All!

10. DY signal Akio Ogawa, Iowa 2010 pythia6.222, p+p @ sqrts=500
DY process, 4M events/6.7E-05mb ~ 60/pb
e+/e- energy>10GeV & h>2
xF>0.1 (25GeV)
4GeV < invariant mass < 10GeV
Everything h>2
14799 events
FMS closed
(FHC cannot
be placed due
To DX magnet)
6512 events
FMS open (x=50cm)
+ FHC (x=60cm)
1436 events
(1/5 from closed)
Inv Mass E pT

11. SPACAL type at STAR, Conceptual Parameters.
Eff. Radiation Length mm
Eff. Rm mm
Eff. Nucl. Int. Length cm
Density g/cm^3
Sampling Fraction %
Depth Int. length
Granularity (eff. Radius) 39mm
Does not required, and does not fit.
Should be optimized, MC
Should it be better?
Optimization, MC

12. SPACAL type at STAR, conceptual parameters, cont.
Resolutions (em. and had.) ,probably, may be degraded.
(Caution, E864 got it naturally… will happen naturally because of reduced depth). Also, FMS+HCAl will have, probably, resolutions factor of two worse compare to SPACAL.
But, need to understand the impact on e/h rejection.
So far, better to be conservative and not degrade it too much on paper.
Evolution of setup may need to be considered also.
If fiber assemblies can be reused for eSTAR, then granularity has to be improved. This is not driven by improvements in position resolution,
moving lower then 0.1λint will not help for hadronic position resolution.

13. Back to R&D proposal. We want to get proof of principle.
(Resolution and Uniformity)
The way we decided to go is to continue our R&D which we didn’t finish in 2003.
Conservative approach:
Build EMC prototype (“spacardeon”).
Readout with PMTs.
Test it with the beam!

14. We started with very simple “dry” version 4X4 matrix readout by APDs and mesh PMTs
We tested it with the beam at SLAC in 2003, and found that it is too simple…
That forced us to think a bit more and change technique to “wet”.
The second version “spacardeon” has not
been tested with the beam for a lots of
different reasons…

15. Dry prototype was very dense, almost like
pure lead (10.3 g/cm3). It has 496 square
0.25mm x 0.25mm fibers inside a
brass container with walls 62 um thick.
496 instead of 500 and 125 um brass in
the corners explains largest variations in
response during transverse scans (factor of two).
1. Compactness requires very strict tolerances
and homogeneity inside the towers to keep
response uniform.
2. Dead materials and areas need
to be eliminated.
Electromagnetic showers indeed very narrow!

16. Planning for a Test Run 2011.
EMC, “spacardeon type”, matrix 4 x4, readout with PMTs – should be ready by
the end of May. Some upgrades for test setup will be required.

17. Status of spacardeon EM prototype.
1. Fiber assemblies in progress (started mid Feb.) about 16k fibers were processed ~2/3 of total.
2. PMT bases, prototyping done/tested, assembly of 40 new bases in progress.
3. Molding form, prototype in the machine shop. Should be ready for tests next week.
4. DAQ etc. for test run will start probably in April.
5. Beam counters, hodoscopes will start in May – need funding.

18. Status of EMC prototype. New fiber Assemblies.

19. To conclude this part (proof of principle):
4x4 EMC matrix is on track to be build.
Test run request still has to be made.
Options are: FNAL, SLAC, CERN
It will be one day workshop at SLAC next week, may be I’ll go there.
Now let’s go back to SPACAL.

20. SPACAL Type for STAR. Should consider: Available space Magnetic Field
Radiation
Installation/Integration

21. How to build it? Concept. Single container.
Fill row by row with preassembled fibers.
Fill row by row with dry powder.
To reconfigure, drain the powder. Re-use fibers if possible (if they will survive).
Lots of questions….

22. What to use? Ideally, square BCF-20 fibers. K12 filter.
Readout with APDs (10 x 10 mm) Hamamatsu.
For prototype, round BCF12, K12 to match existing meshes, readout with the same PMTs which will be used for EMC prototype.

23. What to look at?
Build prototype same way as it can be done for STAR. (Single container, preassembled fibers, fill with powder right at the test run)
Measure energy resolution for electrons.
Disassemble by pouring powder back into buckets.
Response for hadrons probably will have little sense. Due to small size of the device.

24. SPACAL for STAR, Stand alone MC (GEANT 4) Investigate:
1. Pi/gamma separation
2. e/h rejection
As a function of detector parameters.
Later, parameterization of response for electrons and hardrons.
Jay Dunkelberger (UCLA Graduate student) started in Jan.2011
Steep learning curve. First step done, reproduced energy resolution for previous ScFi MC (NIM A 364, 124).

25. MC current model. Parameters: Total length, Granularity, Resolutions
Fiber and absorber composition close to RD1,
Compensated HCAL. Fiber spacing 1 mm, fiber
Diameter 0.47 mm <- to match standard meshes.
Tower lateral dimensions 2.55 cm x 2.55 cm
715 fibers per tower. Length 1.3 m (~ 6 int. lengths)
400 towers in total.
Sc. block at the end of the tower to model fiber
bundles (2 cm x 1 cm x 1 cm).
Tail catcher granularity 4 x 4 towers.
To do: cuts optimization, basics with em. showers (energy, position resolutions vs E). Pi/gamma
Separation.
Later: hadronic showers. How well reproduces experimental results (compensation, etc…), then
e/h rejection

26. SPACAL, Want to move from concept to something real…
Timescale (aggressive):
Obtain fibers – 6 weeks
Process fibers/meshes – 4 weeks (2 weeks)
Scenarios:
If EIC R&D funds will be available? in May???
This will put us on collisions with STAR BEMC and now
FMS maintenance and startup for Run 12!
Ideally want to finish with Test Run in August.

27. Budget Proposal for FY11.
The End !